Sydney
19.2 Leakage to landscape

Supporting information

a. Urban water supply system overview

The urban water supply system is one of three sub-components of Sydney's urban water system.  The three sub-components are the:

  • Urban water supply system
  • Wastewater system
  • Recycled water system.

There are two main sources of water for Sydney's urban water supply system:

  • surface water (11.12)
  • desalinated water (11.6).

Urban water consumption (19.4) was 489,557 ML during the 2011–12 year, representing 48% of all urban water supply system outflows. The remaining urban water was reported as being lost through leakage to landscape (19.2) and operational losses (19.20).

The following figure shows all the inflows and outflows associated with the urban water supply system.

For more detail on a particular flow associated with the urban water supply system, refer to the line item notes.


The Sydney region's urban water supply system using data from Sydney Water Corporation, Shoalhaven City Council and Wingecarribee Shire Council
The Sydney region's urban water supply system using data from Sydney Water Corporation, Shoalhaven City Council and Wingecarribee Shire Council

b. Leakage to landscape

Volumes shown in the following table have been recorded as leakage from the urban water system to the landscape. The total volume of leakage from the urban water supply system was 42,987 ML.


Breakdown table of leakage volumes from each urban utility

Water authority

Recorded leakage volume from urban system to landscape (ML)

Shoalhaven City Council

283

Sydney Water Corporation

42,241

Wingecarribee Shire Council

463

Total

42,987

 

Data on leakage from the urban water system to the landscape are not available for the systems operated by other water utilities.

 

Quantification approach

Shoalhaven City Council

Data source

New South Wales Water Supply and Sewerage Performance Monitoring Report 2011–12.

Provided by

Shoalhaven City Council.

Method

The number provided by the council is the total loss and leakage from the urban potable water supply and non-potable water (raw water diverted from the rivers) supply systems. This volume was estimated as 9% of the total consumption via the urban potable water and non-potable water supplies.


Assumptions, limitations, caveats and approximations

  • Data represents total leakage and loss from potable and nonpotable water supply systems, as the breakdown between the two supplies is not available.
  • Total volume of estimated loss and leakage from the urban water supply system is to be taken as an input to the landscape water store, as the breakdown of leakage components entering landscape and groundwater stores are not available separately.
  • The uncertainty estimate is based on the total leakage factor for the whole of the area managed, and may not specifically relate to the City Council area within the Sydney region (i.e. the value provided is likely to be an overestimate).

Uncertainty information

The volume is based on measured data from a sample area and extrapolated to other areas. Estimated uncertainty based on meter accuracy, professional judgment and organisational practice is +/– 5%.

Sydney Water Corporation

Data source

Tables 7 of Sydney Water Corporation's Water Efficiency Report 2011-12.

Provided by

Sydney Water Corporation.

Method

Sydney Water Corporation used the global water balance approach to determine leakage and loss from the potable water supply system. The water balance is a reconciliation of the volume of water produced by the water treatment plants with all known and estimated end uses. The remainder is classified as leakage.

Assumptions, limitations, caveats and approximations

  • Data represents total leakage and loss from potable and nonpotable water supply systems, as the breakdown between the two supplies is not available.
  • Total volume of estimated loss and leakage from the urban water supply system is to be taken as an input to the landscape water store, as the breakdown of leakage components entering landscape and groundwater stores are not available separately.

Uncertainty information

Measured and estimated data used in the water balance for the calculation contribute to uncertainty of leakage volumes. As leakage volumes calculated via a water balance are proportionally small, residual errors tend to be magnified. The uncertainty band on leakage as calculated by an annual water balance is estimated to be about +/– 25% with a 95% confidence limit.

Wingecarribee Shire Council

Data source

Data spreadsheets.

Provided by

Wingecarribee Shire Council.

Method

The value represents the total volume of leakage and losses from the potable water supply system. The volume is based on the water balance method, where potable water production figures from the water treatment plants are configured with the consumption figures obtained by flow meter readings at listed properties.

Assumptions, limitations, caveats and approximations

  • Data represents total leakage and loss from potable and nonpotable water supply systems, as the breakdown between the two supplies is not available.
  • Total volume of leakage is based on an estimated 11% loss from the system.

Uncertainty information

The volume is based on measured data. Estimated uncertainty based on meter accuracy, professional judgment and organisational practice is +/– 20%.